Illumination device

ABSTRACT

An illumination device is specified which comprises an optoelectronic component having a housing body and at least one semiconductor chip provided for generating radiation, and a separate optical element, which is provided for fixing at the optoelectronic component and has an optical axis, the optical element having a radiation exit area and the radiation exit area having a concavely curved partial region and a convexly curved partial region, which at least partly surrounds the concavely curved partial region at a distance from the optical axis, the optical axis running through the concavely carved partial region

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is the National Stage of International Application No.PCT/DE2006/000314, filed on Feb. 21, 2006, which claims the priority toGerman Patent Applications Serial No. 102005009067.2, filed on Feb. 28,2005 and Serial No. 102005020908.4, filed on May 4, 2005, The contentsof all applications are hereby incorporated by in their entireties.

FIELD OF THE INVENTION

The invention relates to an illumination device having a semiconductorchip provided for generating radiation.

BACKGROUND

Illumination devices of this type are often used for illuminating planarareas. Conventional semiconductor chips often have a comparativelynarrow-angled emission characteristic, so that a large part of theradiation generated by the semiconductor chip is emitted into acomparatively narrow solid angle range. A large-area illumination with asemiconductor chip of this type is made more difficult on account of thenarrow-angled emission characteristic of the semiconductor chip. Anoptical element can be used to widen the emission characteristic.

An optical element of this type is described in U.S. Pat. No. 4,907,044,for example. The semiconductor chip is in each case surrounded by theoptical element by moulding. FIG. 4 of U.S. Pat. No. 4,907,044 shows aradial LED with an optical element of this type, while FIG. 8 shows aso-called overmould LED design with the optical element. In bothdesigns, firstly the semiconductor chip is contact-connected on theconnections and subsequently surrounded by the optical element, theovermould design, in contrast to the radial design, being suitable forsurface mounting. On account of the semiconductor chip beingencapsulated on all sides by the optical element, there is an increasedrisk of damage to the optical element in the case of these designs withhigh radiation power, for instance on account of the heat loss arisingduring the generation of radiation. Accordingly, the components shown inU.S. Pat. No. 4,907,044 are of only limited suitability for high-powerapplications for generating high radiation powers with a correspondinglyhigh lost heat.

SUMMARY

It is an object of the present invention to specify an improvedillumination device.

In a first embodiment, an illumination device according to the inventioncomprises an optoelectronic component having a housing body and at leastone semiconductor chip provided for generating radiation, and a separateoptical element, which is intended for fixing at the optoelectroniccomponent and has an optical axis, the optical element having aradiation exit area and the radiation exit area having a concavelycurved partial region and a convexly curved partial region, which atleast partly surrounds the concavely curved partial region at a distancefrom the optical axis, the optical axis running through the concavelycurved partial region.

The optoelectric component can advantageously be formed essentiallyindependently of the separate optical element. As a consequence, theoptoelectronic component can be optimized in a simplified manner towardhigh-power applications for generating a high radiation power withoutincreasing the risk of damage to the optical element on account of thehigh lost heat.

In one preferred refinement, the semiconductor chip is embodied as athin-film semiconductor chip. In the context of the application, athin-film semiconductor chip is regarded as a semiconductor chip duringwhose production the growth substrate onto which a semiconductor layersequence which a semiconductor body of the thin-film semiconductor chipcomprises has been grown, for example epitaxially, is thinned or, inparticular completely, stripped away. The semiconductor body ispreferably arranged on a carrier which mechanically stabilizes thesemiconductor body said carrier being particularly preferably differentfrom the growth substrate for the semiconductor layer sequence of thesemiconductor body.

The carrier of the thin-film semiconductor chip is advantageously notsubject to the comparatively high requirements that have to be fulfilledby a growth substrate, for instance with regard to the crystalstructure. The degrees of freedom in the selection of the carrier areadvantageously increased compared with the degrees of freedom in theselection of the growth substrate. By way of example, the carrier may bechosen comparatively freely with regard to thermal properties, such as acoefficient of thermal expansion adapted to the semiconductor body or ahigh thermal conductivity. A high thermal conductivity is of particularsignificance in high-power applications in which a critical quantity ofheat is generated in the semiconductor chip during operation of thesemiconductor chip. If the quantity of heat generated in thesemiconductor chip is not dissipated sufficiently from the semiconductorchip, then the risk of damage to the semiconductor chip is increased.This risk can advantageously be reduced by the use of a carrier having ahigh thermal conductivity which is different from the growth substrate.

In a further embodiment, an illumination device according to theinvention comprises a semiconductor chip provided for generatingradiation, and an optical element having an optical axis, thesemiconductor chip being embodied as a thin-film semiconductor chip, theoptical element having a radiation exit area and the radiation exit areahaving a concavely curved partial region and a convexly curved partialregion, which at least partly surrounds the concavely curved partialregion at a distance from the optical axis, the optical axis runningthrough the concavely curved partial region.

Such shaping of the radiation exit area of the optical elementfacilitates the variation of the emission characteristic of theillumination device, so that the radiation power coupled out from theillumination device at an angle with respect to the optical axis isincreased compared with the emission characteristic of the componentwithout an optical element. In particular the convexly curved partialregion contributes to this, this partial region increasing theproportion of radiation coupled out from the illumination device atlarge angles with respect to the optical axis. The illumination devicehaving such an optical element is accordingly particularly suitable forthe homogeneous illumination of a comparatively large, in particularplanar, area including area regions that are offset laterally withrespect to the optical axis. The illumination device is preferablyprovided for the backlighting of a display device, for instance an LCD(liquid crystal display).

In one preferred refinement, the illumination device comprises anoptoelectronic component having a housing body and the semiconductorchip, the optical element being embodied as a separate optical elementand the optical element being provided for fixing at the optoelectroniccomponent.

In a further preferred refinement, the optical axis, in particular ofthe optical element fixed at the optoelectronic component, runs throughthe semiconductor chip. The semiconductor chip may be arranged inparticular in centred fashion with regard to the optical axis. Such anarrangement of the semiconductor chip facilitates homogeneous beamshaping of the radiation generated by the semiconductor chip by means ofthe optical element.

In a further preferred refinement, the optical element is embodied inrotationally symmetrical fashion with respect to the optical axis. Thisadvantageously results in an emission characteristic of the illuminationdevice which is uniform and homogeneous azimuthally with respect to theoptical axis.

In a further preferred refinement, the convexly curved partial regionhas a curvature which is less than a curvature of the concavely curvedpartial region. The homogeneous illumination of area regions to beilluminated by means of the illumination device at a comparatively largedistance from the optical axis is facilitated.

Furthermore, the surface area of the convexly curved partial region ofthe radiation exit area may be greater than the surface area of theconcavely curved partial region. Radiation emerging from the opticalelement in the region of the concavely curved partial regionhomogeneously illuminates a region of the area to be illuminated whichcrosses the optical axis, while the radiation emerging from the convexlycurved partial region is embodied for the homogeneous illumination ofregions at a distance from the optical axis. Since area regions at adistance from the optical axis are often larger than the regionssurrounding the optical axis, the homogeneous illumination of the arearegions at a distance from the optical axis is facilitated by means ofan enlarged area content of the convexly curved partial region comparedwith the area content of the concavely curved partial region. Atransition region between the convexly curved partial region and theconcavely curved partial region is preferably embodied in such a waythat the convexly curved partial region and the concavely curved partialregion have, in particular exclusively, common tangents in thetransition region. Inhomogeneities in the local radiation power orintensity distribution on the area to be illuminated can thus be reducedor avoided. The radiation exit area of the optical element may beembodied in a manner free of edges and/or overall as a differentiablesurface.

Furthermore, in the case of the invention, the optical element may beformed in such a way that two, in particular arbitrary, beams emergingfrom the optical element on the part of the radiation exit area proceedwithout any intersections, that is to say that said beams do notintersect or cross one another. The formation of regions on theilluminated area which are illuminated with an increased radiation powercompared with adjacent regions can thus be avoided. In particular, thelocal distribution of the radiation power on the area to be illuminatedmay be independent of the distance between the area and the illuminationdevice.

Furthermore, the optical element may be embodied in such a way that thebeam shaping by or the beam guidance in the optical element is effectedin a manner free of total reflection. The production tolerances for theoptical element are thus increased.

In a further preferred refinement, the convexly curved partial region isembodied in accordance with a convex lens and the concavely curvedpartial region is embodied in accordance with a concave lens.

In a further preferred refinement, the convexly curved partial regionhas a first region and a second region, the curvature of the firstregion being less than the curvature of the second region. The secondregion is preferably further away from the optical axis or from theconcavely curved partial region than the first region. Thisadvantageously makes it possible to increase the radiation power or theproportion of radiation emerging from the optical element at acomparatively large angle with respect to the optical axis via the moregreatly curved second region.

In a further preferred refinement, the curvature of the convexly curvedpartial region, in particular the curvature of the second region,increases with increasing distance from the concavely curved partialregion. The curvature may increase continuously, in particular.

An increase in the curvature of the convexly curved partial region withincreasing distance from the concavely curved partial region makes itpossible to increase the angle with respect to the optical axis at whichradiation is coupled out from the convexly curved partial region. Ahomogeneous illumination of partial areas of the area to be illuminatedwhich are at a comparatively large distance from the optical axis isthus facilitated.

In a further preferred refinement, the housing body is prefabricated andthe semiconductor chip, after the prefabrication of the housing body, issubsequently arranged at or in the housing body. The housing body isprefabricated in particular before the semiconductor chip is arranged inthe housing body. Compared with the semiconductor chip being formedaround with a radiation-transmissive optical element, such as, forinstance, in the case of the radial LEDs or overmould designs mentionedin the introduction, the risk of damage to the semiconductor chip or thecontact-connection of the semiconductor chip, such as a sensitivebonding wire, is advantageously reduced when the housing body isprefabricated.

In a further preferred refinement, the optoelectronic component has aleadframe which is formed around, in particular a leadframe around whichthe housing body is formed, for example by moulding or casting. Theleadframe may be surrounded by the housing body by moulding for exampleby means of injection moulding, transfer moulding or compressionmoulding. The housing body may contain a plastic. The optoelectroniccomponent may accordingly have a prefabricated housing comprising thehousing body and the leadframe. In particular, the housing may beembodied as a so-called premoulded housing design. In the case of adesign of this type, the semiconductor chip is mounted onto theleadframe after the production of the housing.

In a further preferred refinement, the optoelectronic component, inparticular the leadframe, has a first electrical connection part, asecond electrical connection part and a thermal connection part, whichin particular is formed separately from the electrical connection parts.Electrical contact can be made with the semiconductor chip via theelectrical connection parts. The thermal connection part enables a goodthermal linking to an external heat conducting device, for instance aheat sink, independently of the electrical contact-connection of theoptoelectronic component by means of the electrical connection parts.The electrical connection parts may be electrically conductivelyconnected, in particular soldered to conductor tracks of a circuitboard, for example. The thermal connection part may be thermallyconductively connected, for instance by means of soldering to theexternal heat conducting device, for example, the external heatconducting device being preferably electrically insulated from theconductor tracks.

In one advantageous development, the electrical connection parts and thethermal connection part are in each case at least partly part of anenveloping area that completely envelopes the surface of the housingbody on the part of different side areas of the surface of the housingbody. In particular, the electrical connection parts and the thermalconnection part may emerge from the housing body on the part ofdifferent side areas or form a part of the surface of the housing bodyat different side areas. Preferably, the electrical connection parts onthe part of in each case different side areas of the surface of thehousing body in each case also form at least partly a part of anenveloping area that completely envelopes the surface of the housingbody. A separate electrical and thermal connectability by means of theelectrical connection part and the thermal connection part,respectively, is thus facilitated.

In a further preferred refinement, the optoelectronic component isembodied as a surface-mountable component (SMD: Surface MountableDevice). Surface-mountable components are distinguished by particularlysimple manageability, particularly during mounting on a circuit board.They may for example be positioned on a circuit board by means of asimple “pick and place” process and subsequently be electrically and/orthermally connected. Furthermore, the illumination device with theoptical element mounted at the optoelectronic component may be embodiedin surface-mountable fashion. During the mounting of the device, therisk of damage to the optical element, for instance on account of thehigh soldering temperature, is advantageously not critically increased.

In a further preferred refinement, a mirror layer is arranged on thesemiconductor body, in particular between the semiconductor body and thecarrier. Radiation generated in the semiconductor body can be reflectedfrom the mirror layer, as a result of which the radiation power emergingfrom the semiconductor body on the opposite side to the mirror layer canadvantageously be increased. Furthermore, the mirror layer preventsabsorption of radiation in structures, such as an absorbent carrier, forinstance, arranged on the opposite side of the mirror layer to thesemiconductor body. The degrees of freedom in the selection of thecarrier are thus increased more extensively.

Preferably, the mirror layer contains a metal or the mirror layer isessentially embodied in metallic fashion. By way of example, the mirrorlayer contains Au, Al, Ag, Pt, Ti or an alloy with at least one of thesematerials. Au, for example, is distinguished by a high reflectivity inthe red spectral range, while Ag or Al also exhibits a high reflectivityin the blue or ultraviolet spectral range.

In a further preferred refinement, the optical element has at least onefixing element provided for fixing the optical element at theoptoelectronic component. The fixing element may be fitted, for instanceadhesively bonded, to a prefabricated optical element. Furthermore, thefixing element may be formed jointly with the optical element during theproduction of the optical element. In the latter case, the opticalelement and the fixing element may be embodied in one piece. The opticalelement may be casted or moulded, for example. By way of example, inparticular an injection moulding, transfer moulding or compressionmoulding method is suitable for this purpose.

In this respect, it should be noted that the configuration of theoptical element that is preferably rotationally symmetrical with respectto the optical axis which is mentioned further above essentially relatesto the optical functional areas, that is to say those elements of theoptical element which are provided for beam shaping or beam guidance.Elements which principally do not serve for beam shaping, such as thefixing element, need not necessarily be embodied in rotationallysymmetrical fashion with respect to the optical axis.

Preferably, the optical element is formed such that it can be pluggedonto the optoelectronic component. A pin-like fixing element isparticularly suitable for this.

The optical element preferably contains a reaction resin, for instancean epoxy resin or an acrylic resin, a silicone resin or a silicone. Theoptical element may furthermore contain a thermoplastic material.Furthermore, the optical element is preferably embodied as a rigid bodywhich is plastically deformable in particular only with additionalmeasures, such as, for instance, heating or considerable expenditure offorce.

In a further preferred refinement, the fixing element is arranged on thepart of a radiation entrance area of the optical element.

In a further preferred refinement, the optoelectronic component, inparticular the housing body, has at least one fixing device. The opticalelement can be fixed at the optoelectronic component by means of theinteraction of the fixing element with the fixing device. For thispurpose, the fixing device is expediently formed as a counterpart to thefixing element. The fixing element for fixing the optical element at theoptoelectronic component preferably engages into the fixing device.

In a further preferred refinement of the invention, the optical elementis provided for fixing by means of press fit, hot press fit, caulking,hot caulking, thermal riveting or adhesive bonding at the optoelectroniccomponent.

In the case of a press fit, the optical element is fixed at thecomponent by means of the pressure exerted by the fixing element of theoptical element and the fixing device of the optoelectronic component onone another. Said pressure preferably acts essentially along the normalto the surface of the fixing element and of the fixing device,respectively.

In the case of the hot press fit, the fixing element is heated in such away that although it is not flowable, and in particular is dimensionallystable without additional force action, it is nevertheless plasticallyshapeable. The heated fixing element shapes itself to the fixing deviceunder the action of force. After the fixing element has cooled down, theoptical element is fixed mechanically stably at the optoelectroniccomponent.

In the case of caulking, the fixing element and/or the fixing deviceexperiences a mechanically produced deformation, if appropriate inaddition to a press-fitting pressure. For this purpose, the fixingelement and/or the fixing device is deformed for example by means of adeformation tool, for instance a needle, in such a way that the opticalelement is fixed mechanically stably at the optoelectronic component.The deformation may be effected in particular punctiform or in regions.In the case of hot caulking, the deformation tool is additionallyheated, so that the fixing element becomes plastically shapeable and/orflowable in the region of contact with the tool. The expenditure offorce can be reduced in the case of hot caulking compared with caulking.

In the case of adhesive bonding, the fixing is effected by means of anadhesive bond which is formed, for instance by means of an adhesionpromoting material, between the fixing element and the fixing device.

In the case of thermal riveting, the fixing element is heated,preferably in a partial region, in such a way that it becomes flowableand flows onto the optoelectronic component, in particular the housingbody and/or the fixing element of the housing body, and cures as itcools down, a mechanically stable fixing being formed thereafter.

In a further preferred refinement, the optical element has at least oneguide element. The guide element may facilitate the mounting of theoptical element at the optoelectronic component. The guide element ispreferably embodied in such a way that the fixing element is guided tothe fixing device by means of the guide element in the case of aslightly misaligned arrangement with regard to the fixing device. Suchguidance may preferably be obtained by means of the inherent weight ofthe optical element or a pressure exerted by means of a mounting tool.The optical element may “slip” onto the optoelectronic component inparticular with guidance by the guide element, the guide elementpreferably being formed in such a way that the fixing element engagesinto the fixing device or “slips” into the fixing device. Furthermore,the guide element is preferably in direct, in particular mechanical,contact with the housing body when guiding the fixing element to thefixing device and/or after the mounting of the optical element has beenconcluded.

Preferably, the guide element, compared with the fixing element, isarranged closer to an edge delimiting the optical element on the part ofthe fixing element. After the fixing of the optical element at theoptoelectronic component, preferably at least part of the housing bodyis arranged between the guide element and the fixing element.

In particular, the guide element may be arranged outside the housingbody and may extend for example in the vertical direction along a sidearea of the housing body. The guide element is preferably in directcontact with the side area.

In a further preferred refinement, the guide element is embodied inbevelled fashion or in chamfered fashion in particular on a side remotefrom the edge that delimits the optical element on the part of thefixing element. Such bevelling or chamfering makes it possible tofacilitate the “slipping” of the optical element onto the housing bodyof the optoelectronic component or the “slipping” of the fixing elementinto the fixing device.

In a further preferred refinement, the optical element has a pluralityof fixing elements and/or guide elements. The mechanical stability ofthe fixing and the positional stability of the mounted optical elementrelative to the semiconductor chip can thus be increased on account of aplurality of fixing elements. A plurality of fixing elements facilitatesthe fixing of the optical element at the optoelectronic component.Furthermore, the guide elements may also contribute to the mechanicalstability or to the positional stability of the optical element. Inparticular, the risk of damage to the optical element, for instance onaccount of shear forces acting on the illumination device, can bereduced by means of the guide elements.

In a further preferred refinement, an intermediate layer is arrangedbetween the optical element fixed at the optoelectronic component andthe semiconductor chip.

In a further preferred refinement, the intermediate layer is plasticallyshapeable. A plastically shapeable material for the intermediate layercan be provided on the optoelectronic component prior to the mounting ofthe optical element at the optoelectronic component. During the mountingof the optical element at the optoelectronic component, a pressure canbe exerted on the shapeable material by means of the optical element insuch a way that the material is distributed in the lateral directionduring the fixing of the optical element and the intermediate layer isformed. The intermediate layer may, in particular directly, adjoin theoptical element, for instance on the part of the radiation entranceside. Furthermore, the material for the intermediate layer is preferablydimensionally stable without the action of force. An uncontrolleddeliquescence of the material before the action of force is thusavoided.

In a further preferred refinement, an interspace is formed between theoptical element fixed at the optoelectronic component and theoptoelectronic component, in particular between that side of the housingbody which faces the optical element and the radiation entrance area.

In a further preferred refinement, the intermediate layer contains asilicone, in particular a silicone gel. A silicone is particularlysuitable as material for the intermediate layer.

Preferably, the interspace is provided as a gap or joint for receivingthe intermediate layer in the event of an expansion of the intermediatelayer. If the intermediate layer expands, for example on account ofheating, then the intermediate layer can expand into the joint withoutsignificantly increasing the mechanical loading on the optical elementor the optoelectronic component. In the course of cooling down, theoptical element can withdraw from the joint. The interspace ispreferably formed between the optical element and that region of thehousing body which has the smallest distance from the optical element.

In particular, the radiation entrance area may be spaced apart from thehousing body over its whole area. This may be achieved by forming thefixing element in a suitable manner.

In a further preferred refinement, the semiconductor chip is embedded inan encapsulation, which, in particular, is transmissive to the radiationgenerated by the semiconductor chip. The encapsulation may contain forexample reaction resin, such as an acrylic or epoxy resin, a siliconeresin or a silicone. The encapsulation is preferably formed in rigidfashion, in particular compared with the intermediate layer, in ordernot to increase the risk of damage to the chip or the chipcontact-connection, which may be effected for example by means of abonding wire which is preferably likewise embedded in the encapsulation.

In a further preferred refinement, the intermediate layer is formed as arefractive index adaptation layer. Excessive jumps in refractive index,which would lead to correspondingly high reflection losses of radiationgenerated by the semiconductor chip at the respective interfaces, canthus be avoided. The intermediate layer particularly preferably reducesjumps in refractive index which the radiation generated by thesemiconductor chip experiences between the exit from the encapsulationand the entrance into the optical element. The intermediate layerparticularly preferably reduces the jump in refractive index comparedwith an air-filled free space instead of the intermediate layer. Theintermediate layer advantageously improves the optical linking of theoptical element to the optoelectronic component.

The intermediate layer may furthermore be embodied in adhesion-promotingfashion, thereby advantageously improving the mechanical linking of theoptical element to the optoelectronic component.

In a further preferred refinement, the intermediate layer adjoins theencapsulation and the optical element. The intermediate layer preferablycovers that region of the optical element in which radiation generatedby the semiconductor chip couples into the optical element.

The encapsulation is preferably covered, in particular completely, withthe intermediate layer in the radiation exit region of theencapsulation.

Further features, advantageous refinements and expediences of theinvention emerge from the following description of the exemplaryembodiments in conjunction with the figures.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a schematic sectional view of a first exemplary embodimentof an illumination device according to the invention,

FIG. 2 shows a schematic sectional view of a semiconductor chip that isparticularly suitable for an illumination device,

FIG. 3 shows an example of an emission characteristic of an illuminationdevice according to the invention,

FIG. 4 shows, in FIGS. 4A to 4F, different schematic views of an opticalelement that is particularly suitable for an illumination deviceaccording to the invention,

FIG. 5 shows a schematic plan view of a further optical element that isparticularly suitable for an illumination device according to theinvention,

FIG. 6 shows a schematic sectional view of a second exemplary embodimentof an illumination device,

FIG. 7 shows, in FIGS. 7A and 7B, different schematic views of anoptoelectronic component that is particularly suitable for anillumination device,

FIG. 8 shows, in FIGS. 8A to 8D, different schematic views of anoptoelectronic component in accordance with FIG. 7 and of a thirdexemplary embodiment of an illumination device according to theinvention.

Elements that are identical, of identical type and act identically areprovided with identical reference symbols in the figures.

DETAILED DESCRIPTION

FIG. 1 shows a schematic sectional view of a first exemplary embodimentof an illumination device according to the invention

The illumination device 1 comprises an optical element 2 and asemiconductor chip 3 provided for generating radiation.

A radiation exit area 4 of the optical element 2 has a concavely curvedpartial region 5, through which the optical axis 6 of the opticalelement runs, and a convexly curved partial region 7 surrounding theconcavely curved partial region at a distance from the optical axis. Theconvex partial region and the concave partial region may be embodied inparticular in accordance with a convex or concave lens.

Radiation emitted in an active zone 303 of the semiconductor chip 3arranged on the optical axis 6 enters into the optical element 2 via aradiation entrance area 8, which is preferably embodied in planarfashion. The radiation, in particular visible radiation, generated bythe semiconductor chip is illustrated in FIG. 1 by the lines which areidentified with arrows and symbolize individual light rays.

The optical element 2 is formed for the homogeneous illumination of anarea 9, for instance of a diffuser film or for a display device, such asan LCD. The optical axis preferably runs through the area 9. The area 9particularly preferably runs essentially perpendicular to the opticalaxis 6.

The optical element is formed for the homogeneous illumination of thearea 9. Through suitable formation of the curvatures of the convexlycurved partial region and of the concavely curved partial region, theradiation generated by the semiconductor chip can be distributed on theradiation exit side in such a way that the area 9 is illuminateduniformly and homogeneously by means of the illumination device.Preferably in each case essentially the same radiation power impinges ondifferent, equally sized regions of the area.

Radiation emerging via the concave partial region 5 is spread in amanner similar to that in the case of a diverging lens. In particular,radiation impinging on the radiation exit area at an angle that differsfrom 90° with respect to the optical axis is refracted away from theoptical axis upon entering into the optical element. The radiationemerging from the concave partial region serves for homogeneouslyilluminating a region of the area 9 that surrounds the optical axis 6.For the illumination device to have an emission characteristic which isuniform azimuthally peripherally around the optical axis 6, the opticalelement is preferably embodied in rotationally symmetrical fashion withrespect to the optical axis 6.

Regions of the area 9 which are spaced apart comparatively far from theoptical axis are illuminated by means of radiation that emerges from theoptical element 2 via the convexly curved partial region 7 at an anglethat differs from 90° with respect to the optical axis 6. The transitionregion between the concave partial region and the convex partial regionis preferably smooth, in particular is formed in a manner free of edges.In particular, the radiation exit area may be embodied in differentiablefashion, preferably over the whole area. A homogeneous illumination ofthe area 9 is thus facilitated.

The convexly curved partial region of the radiation exit area preferablyhas a larger area content than the concavely curved partial region. As aconsequence, compared with the concavely curved partial region, anincreased proportion of radiation emerges from the optical element viathe convexly curved partial region.

Furthermore, the convexly curved partial region preferably has a firstregion 71 having a first curvature and a second region 72 having asecond curvature. In this case, the first curvature is preferably lessthan the second curvature.

On account of the greater curvature in the second region 72, radiationemerging from the optical element 2 in the second region isadvantageously at a greater angle with respect to the optical axis 6than radiation emerging from the optical element in the first region 71or in the concave partial region 5. The homogeneous illumination ofregions of the area 9 that are comparatively far away from the opticalaxis is thus facilitated.

Preferably, radiation from the optical element emerges from the opticalelement only at an angle of less than 90° with respect to the opticalaxis. The illumination device radiates in particular laterally ortransversely with respect to the optical axis and forward, in thedirection of the optical axis. The illumination device 1 is preferablyembodied in such a way that a large part of the radiation power emergesfrom the optical element at an angle with respect to the optical axis,in particular via the convexly curved partial region.

The curvature of the convex partial region may increase with increasingdistance from the concavely curved partial region, in particular in thesecond region 72 in the direction of the radiation entrance area 8,thereby facilitating an increased coupling-out of radiation at largeangles with respect to the optical axis and thus the illumination ofregions of the area 9 that are comparatively far away from the opticalaxis.

The illumination device 1 may be embodied in such a way that beamsemerging from the optical element do not overlap, so that the localradiation power distribution on the area to be illuminated isessentially independent of the distance between the area and theillumination device.

If the optical element brought about a crossover of beams in the case ofbeam shaping, then a focal region could be formed, so that the localradiation power distribution on the area would be dependent on thedistance between the area and the optical element. Upon variation of thedistance between the area 9 and the optical element 2 inhomogeneities,for instance rings of higher intensity, in the local radiation powerdistribution would be formed. Said inhomogeneities are brought about bya crossover of beams. In the case of the optical element shown in FIG.1, however, on account of the radiation running in a manner free ofintersections, the local distribution of the radiation power on the area9 is independent of the distance between the area and the opticalelement 2. Furthermore, the beam shaping or the beam guidance in theoptical element is preferably effected in a manner free of totalreflection.

The optical element is preferably formed as a separate optical elementintended for fixing at an optoelectronic component comprises thesemiconductor chip. The optoelectronic component can thus be optimizedindependently of the optical element for a high-power application andsubsequently be provided with the separate optical element. Theindividual components of the illumination device can therefore beproduced in a manner optimized independently of one another for theirrespective main function, beam shaping in the case of the opticalelement and generation of radiation in the case of the component.

The semiconductor chip 3 is furthermore preferably embodied as athin-film semiconductor chip. A semiconductor body 302 of thesemiconductor chip 3, which comprises a semiconductor layer sequencewith the active zone 303, is arranged on a carrier 301, which isdifferent from a growth substrate on which the semiconductor body, inparticular the semiconductor layer sequence, was grown, preferablyepitaxially. Accordingly, the carrier 301 does not have to meet the highrequirements for a growth substrate, but rather may be embodied in amanner optimized for example with regard to the heat dissipationproperties. A thin-film semiconductor chip in the case of which thegrowth substrate is stripped away during production is accordinglyparticularly suitable for high-power applications with a comparativelyhigh heat loss arising in the semiconductor chip.

FIG. 2 illustrates an exemplary embodiment of a semiconductor chip thatis particularly suitable for an illumination device, on the basis of aschematic sectional view.

The semiconductor chip 3, for instance an LED chip, has a semiconductorbody 302 arranged on a carrier 301, said semiconductor body comprising asemiconductor layer sequence with an active zone 303 provided forgenerating radiation. A first contact 304 is arranged on that side ofthe semiconductor body which is remote from the carrier, via whichcontact the semiconductor chip 3 can be electrically connected inconjunction with a second contact 305 arranged on that side of thecarrier which is remote from the semiconductor body. The first contact304 is provided in particular for conductive connection to a bondingwire and the second contact 305 is provided for conductive connection toa connection conductor (in this respect, cf. e.g. the componentsdescribed in connection with FIGS. 6, 7 and 8). The contacts may containfor example in each case a metal or an alloy.

In one preferred refinement, the semiconductor body 302, in particularthe active zone 303, contains at least one III-V semiconductor material,for instance a material from the material systemsIn_(x)Ga_(y)Al_(1-x-y)P, In_(x)Ga_(y)Al_(1-x-y)N orIn_(x)Ga_(y)Al_(1-x-y)As, in each case with 0≦x≦1, 0≦y≦1 and x+y≦1.

III-V semiconductor materials are particularly suitable for generatingradiation in the ultraviolet spectral range (In_(x)Ga_(y)Al_(1-x-y)N)through the visible spectral range (In_(x)Ga_(y)Al_(1-x-y)N, inparticular for blue to green radiation, or In_(x)Ga_(y)Al_(1-x-y)P, inparticular for yellow to red radiation) to the infrared(In_(x)Ga_(y)Al_(1-x-y)As) spectral range. With III-V semiconductormaterials, in particular from the material systems mentioned, highinternal quantum efficiencies can furthermore advantageously be obtainedduring the generation of radiation.

In a further preferred refinement, the active zone 303 comprises aheterostructure, in particular a double heterostructure. Furthermore,the active zone may comprise a single or multiple quantum wellstructure. Particularly high internal quantum efficiencies can beobtained by means of such structures, in particular a multiple quantumwell structure or a double heterostructure.

In the context of the application, the designation quantum wellstructure encompasses any structure in which charge carriers experiencea quantization of their energy states by means of confinement. Inparticular, the designation quantum well structure does not comprise anyindication about the dimensionality of the quantization. It thusencompasses, inter alia, quantum wells, quantum wires and quantum dotsand every combination of these structures.

In a further preferred refinement, a mirror layer 306 is arrangedbetween the semiconductor body 302 and the carrier 301. The mirror layermay be embodied for example as a metal-containing, in particularessentially metallic, mirror layer. Radiation generated in the activezone can be reflected at the mirror layer, thereby preventing absorptionin the structures, for instance the carrier, arranged downstream of themirror layer as viewed from the active zone. The efficiency of thesemiconductor chip 3 can thus be increased. By way of example, themirror layer contains Au, Al, Ag, Pt, Ti or an alloy with at least oneof these materials. Al and Ag have particularly high reflectivities inthe ultraviolet and blue spectral ranges, and Au has a particularly highreflectivity also in the yellow, orange and red to infrared spectralranges. Furthermore, the proportion of radiation emerging at the side ofthe semiconductor body 302 opposite to the mirror layer 306 is increasedas a result of reflection at the mirror layer.

In a further preferred refinement, a connecting layer 307 is arrangedbetween the carrier 301 and the mirror layer 306, by means of whichconnecting layer the semiconductor body is fixed on the carrier on thepart of the mirror layer. The connecting layer 307 may be embodied forexample as a solder layer.

The semiconductor chip 3 shown in FIG. 2 is embodied as a thin-filmsemiconductor chip, which means that during the production of thesemiconductor chip, the growth substrate on which the semiconductorlayer sequence for the semiconductor chip was grown, for example bymeans of epitaxy, is stripped away. Accordingly, the carrier 301 is inparticular different from the growth substrate and does not have tosatisfy the high requirements made for a growth substrate, but rathermay be chosen comparatively freely with regard to further propertiesthat are advantageous for the semiconductor chip, for instance a highthermal conductivity.

The carrier preferably has a comparatively high thermal conductivity. Byway of example, the carrier contains Ge. A GaAs carrier may also beemployed.

The active zone 303 is preferably electrically conductively connected tothe second contact 305 via the electrically conductive carrier, theelectrically conductive connecting layer and the electrically conductivemirror layer and also the semiconductor layer sequence.

If the carrier contains a semiconductor material, then the carrier ispreferably doped in a suitable manner for increasing the conductivity.

In order to produce a thin-film semiconductor chip, by way of example,firstly the semiconductor layer sequence for the semiconductor body 302is produced on the growth substrate. Afterwards, the mirror layer isapplied, for instance by means of vapour deposition, in particularsputtering, onto that side of the semiconductor layer sequence which isremote from the growth substrate. On the part of the mirror layer, thecomposite comprising semiconductor layer sequence and growth substrateis thereupon connected to the carrier 301 by means of the connectinglayer 307, whereupon the growth substrate is removed or stripped away,for instance by means of etching or laser separation.

Thin-film semiconductor chips are distinguished, in particular with amirror layer, by an advantageously high efficiency. Furthermore, athin-film semiconductor chip may have a cosinusoidal emissioncharacteristic essentially corresponding to the one of a Lambertianradiator. A semiconductor chip embodied as a surface radiator may berealized in simplified fashion by means of a thin-film semiconductorchip, in particular with a metal-containing mirror layer.

A thin-film semiconductor chip, for instance a thin-film light-emittingdiode chip, may furthermore be distinguished by the followingcharacteristic features:

-   -   at a first main area of a semiconductor layer sequence which        comprises an active zone, said first main area facing towards a        carrier element, e.g. the carrier 301, a mirror layer is applied        or formed, for instance integrated as a Bragg mirror in the        semiconductor layer sequence, and reflects at least part of the        radiation generated in the semiconductor layer sequence back        into the latter;    -   the semiconductor layer sequence has a thickness in the region        of 20 μm or less, in particular in the region of 10 μm, and;    -   the semiconductor layer sequence contains at least one        semiconductor layer with at least one area having a disordered        structure that ideally leads to an approximately ergodic        distribution of the light in the semiconductor layer sequence,        that is to say it has an as far as possible ergodically        stochastic scattering behaviour.

A basic principle of a thin-film light-emitting diode chip is describedfor example in I. Schnitzer et al., Appl. Phys. Lett. 63 (16), 18 Oct.1993, 2174-2176, the disclosure content of which is in this respecthereby incorporated by reference in the present application.

It should be noted that the illumination device can, of course, berealized not just with a thin-film semiconductor chip. Some othersemiconductor chip, such as, for instance, a semiconductor chip in thecase of which the growth substrate is not stripped away, may also besuitable for an illumination device. However, a thin-film semiconductorchip is particulary suitable on account of the high efficiency and asurface emission which can be obtained in a simplified manner and is,preferably increasingly, directed directly in the direction of theoptical element.

FIG. 3 shows an example of an emission characteristic of an illuminationdevice according to the invention. The relative intensity in percent isplotted as a function of the angle θ in ° with respect to the opticalaxis.

The emission characteristic shown here was determined for an opticalelement 2 in accordance with FIG. 1 which is embodied in rotationallysymmetrical fashion with respect to the optical axis, and asemiconductor chip 3 in accordance with FIG. 2 which was arranged at adistance of 0.6 mm from the radiation entrance area 8.

The illumination device preferably emits a large part of the radiationpower laterally with respect to the optical axis, in particular atcomparatively large angles. The radiation power coupled out in theconcavely curved partial region surrounding the optical axis preferablyhas a local minimum of the characteristic, in particular in the angularrange of between 0° and 10°.

Furthermore, the illumination device preferably emits more than 50%,particularly preferably more than 60°, of the radiation power generatedby the semiconductor chip in an angular range of between 80° and 40°with respect to the optical axis.

The maximum of the intensity is at approximately 70°. Proceeding fromthe concave partial region 5, which corresponds to the region around 0°,the intensity increases as the angle increases, which corresponds to theconvexly curved partial region, for instance in accordance with a powerfunction, in particular in accordance with a parabola, and falls sharplyafter reaching the maximum.

FIG. 4 shows, in FIGS. 4A to 4F, different schematic views of an opticalelement 2 that is particularly suitable for an illumination deviceaccording to the invention. In this case, FIG. 4A shows an oblique viewfrom below of the radiation entrance area 8 of the optical element, FIG.4B shows an oblique view from above of the radiation exit area 4 of theoptical element, FIG. 4C shows a plan view of the radiation entrancearea, FIG. 4D shows a side view, FIG. 4E shows a sectional view alongthe line E-E from FIG. 4C, and FIG. 4F shows a sectional view along theline F-F in FIG. 4C.

The optical element essentially corresponds to the optical element shownin FIG. 1. In contrast to the optical element in accordance with FIG. 1,in the case of which essentially the optical functional regions of theoptical element 2 are shown, the optical element 2 in accordance withthe exemplary embodiment shown in FIG. 4 has a plurality of fixingelements 9 and guide elements 10. Furthermore, the optical element hasat least one orientation element 11, preferably a plurality oforientation elements.

The optical element 2 is formed in particular for fixing at a separateoptoelectronic component having a housing body and the semiconductorchip of the illumination device (in this respect, cf. FIGS. 6, 7 and 8).

The optical element 2 is embodied in radiation-transmissive fashion andcontains for example a radiation-transmissive silicone or a siliconeresin.

The optical element may, if appropriate, also contain a reaction resin,for instance an acrylic or epoxy resin, and/or be embodied insilicone-free fashion. If appropriate, the optical element may contain athermoplastic material or consist of a thermoplastic material.

The optical element is preferably produced by means of injectionmoulding, transfer moulding or compression moulding. The fixing elements9, the guide elements 10 and/or the orientation elements 11 may also beproduced by means of these methods. In particular, the elementsmentioned and the optical element may be formed in one piece. Theoptical element is preferably free of undercuts. It is thus possible todispense with the use of a cost-intensive slide in the mould. In orderto facilitate the mould release of the optical element from the mould,the fixing elements 9, the guide elements 10 and/or the orientationelements 11 may be embodied in bevelled fashion and thus may haveso-called mould release bevels.

The fixing elements 9, the guide elements 10 and/or the orientationelements 11 are preferably arranged on the part of the radiationentrance area 8 of the optical element.

The guide elements 10 are expediently formed in such a way that duringthe fixing of the optical element 2 at the optoelectronic component, thefixing elements, in the case of a slightly misaligned arrangement of thefixing elements relative to the corresponding fixing devices of theoptoelectronic component, slip or are introduced into the correspondingfixing devices of the optoelectronic component or the fixing elementsare guided to the fixing devices. For this purpose, the guide elements10 are embodied in bevelled fashion on their side remote from theradiation entrance area. The guide elements have a chamfer 12 for thispurpose. The guide elements 10 taper in the bevelled region preferablywith increasing distance from the radiation entrance area 8. The guideelements 10 are preferably bevelled on one side, in particular on a sideremote from an edge 13 that delimits the optical element 2 on the partof the radiation entrance area.

The fixing elements 9 are embodied as individual pins in the exemplaryembodiment in accordance with FIG. 4. By way of example, the fixingelements are embodied for press fit and taper, preferably continuously,with increasing distance from the radiation entrance area 8. A diameterof the fixing elements 9 may accordingly decrease with increasingdistance from the radiation entrance area 8.

On the part of the radiation entrance area 8, the optical element 2 isdelimited by the edge 13. The guide elements 10 are arranged closer tothe edge 13 compared with the fixing elements 9. The fixing of theoptical element at the optoelectronic component is thus advantageouslyfacilitated and the overall stability of an illumination device with theoptoelectronic component and the optical element fixed at the latter isincreased.

A fixing element is preferably assigned a plurality of guide elements,for instance two guide elements, as a result of which the fixing of theoptical element at the optoelectronic component is advantageouslyfacilitated more extensively on account of improved guidance during themounting of the optical element. The guide elements assigned to a fixingelement are arranged adjacent, preferably directly adjacent, to thefixing element.

The orientation elements 11 advantageously facilitate the mounting ofthe optical element at the optoelectronic component, in particular theoriented plugging of the optical element onto the component. In amounting tool into which the optical element can be inserted for fixingat the component, orientation devices corresponding to the orientationelements may be provided, into which orientation devices the orientationelements engage, in particular for the mechanically stable, releasablefixing of the optical element in the tool. It is thus possible to ensurethat the optical element is oriented in a predefined manner for mountingin the mounting tool of a placement apparatus. The orientation elementspreferably project beyond the edge 13, as a result of which, inparticular, points of engagement are formed for the tool and themounting is simplified.

Furthermore, the optical element, in a plan view of the radiationentrance area 8, is preferably formed in essentially circular fashion.Furthermore, the optical element, in a plan view of the radiationentrance area 8, is preferably formed axially symmetrically with respectto the axes of symmetry E-E and/or D-D from FIG. 4C and/orcentrosymmetrically with respect to a centre point of the radiationentrance area.

FIG. 5 shows a further exemplary embodiment of an optical element 2 foran illumination device according to the invention, on the basis of aschematic plan view of the radiation entrance area 8 of this opticalelement.

The optical element 2 shown in FIG. 5 essentially corresponds to thatshown in FIG. 4. In contrast to FIG. 4, separate orientation elementsare dispensed with in the optical element in accordance with FIG. 5.Rather, the guide elements 10 are in part also formed as orientationelements 11. The formation of separate orientation elements 11 can thusadvantageously be dispensed with. The guide elements 11 formed asorientation elements preferably project beyond the edge 13.

FIG. 6 illustrates a schematic sectional view of a second exemplaryembodiment of an illumination device according to the invention with anoptical element fixed at an optoelectronic component.

The illumination device 1 has an optoelectronic component 20 comprisingthe semiconductor chip 3. The optical element 2, which is formed forexample in accordance with one of the previous figures, is fixed at theoptoelectronic component 20 by means of the fixing elements 9.

For the fixing of the optical element, fixing devices 201 are formed inthe optoelectronic component 1, the fixing elements 9 engaging into saidfixing devices in the course of fixing. The fixing devices 201 arepreferably formed as cutouts extending from a first main area 202 of ahousing body 203 of the optoelectronic component as far as to a secondmain area 204 opposite to the first main area 202 of the housing body.The cutouts penetrate through the housing body in particular completely.The fixing devices may for example be preformed in the housing body asearly as during the production thereof. By way of example, the fixingdevice is embodied in cylindrical fashion. The fixing devices may, ifappropriate, also be formed as recesses that do not completely penetratethrough the housing body.

The fixing elements 9 are embodied for fixing by means of a press fit.For this purpose, the fixing elements 9 preferably taper with increasingdistance from the radiation entrance area 8 of the optical element 2.The optical element 2 is plugged onto the optoelectronic component, thefixing elements 9 engaging into the fixing devices 201. When the fixingelements come into contact with the housing body, a pressure is exertedon the fixing element, said pressure increasing as the optical elementis pressed further into the fixing device in such a way that the opticalelement is finally fixed in a mechanically stable manner at the housingbody 203 by means of a press fit.

The radiation entrance area 8 of the optical element 2 fixed at theoptoelectronic component 20 is preferably spaced apart from theoptoelectronic component, particularly preferably from the housing body,in particular from the first main area 202 thereof. For this purpose,the fixing elements 9 have, expediently in a region adjacent to theradiation entrance area 8, a larger lateral extent compared with thelateral extent of the fixing devices, in particular in a directionparallel to the first main area.

The distance between the semiconductor chip and the optical element, inparticular the radiation entrance area 8 thereof, may be 1 mm or less. Adistance of 0.6 mm has proved to be particularly advantageous.

It should be noted that not only a press fit is suitable for fixing theoptical element at the optoelectronic component. The methods citedfurther above, hot pressing, caulking, hot caulking, thermal riveting oradhesive bonding, may also be employed, if appropriate with suitablemodification of the fixing elements and/or of the fixing devices.

For thermal riveting, by way of example, after introduction into thefixing device on the part of the second main area 204 of the housingbody 203, the fixing element projects beyond the second main area. Inthe protruding segment of the fixing element 9, the fixing element issubsequently heated in such a way that it becomes flowable at least inthis partial region. The flowable segment shapes itself (flows) onto thefixing device and/or the housing body, so that a mechanically stablefixing of the optical element 2 at the optoelectronic component 20 isformed after the fixing element has cooled down and solidified. Ifappropriate, the housing body may also be heated in the region adjoiningthe fixing elements on the part of the second main area, so that thehousing body and the flowable fixing element melt together.

For thermal riveting on the part of the second main area, the lateralextent of the fixing device 201 is preferably greater than that of thefixing element 9 and particularly preferably decreases in the directionof the first main area 202. That volume of the fixing device which isfree after the introduction of the fixing element into the fixing deviceand is not filled by the fixing element is intended for receiving thematerial projecting beyond the second main area prior to the heating ofthe fixing element. For this purpose, the fixing device is preferablyformed, in the region adjoining the second main area of the housingbody, with an approximately trapezoidal cross section tapering in thedirection of the first main area. After the tapering, the fixing devicemay extend in essentially cylindrical fashion in the direction of thefirst main area.

The optical element 2 may furthermore project laterally beyond sideareas 217 of the housing body. In the projecting region, guide elementsand/or orientation elements may be arranged at the radiation entrancearea 8, which is not accorded an optical function in this region (cf.the explanations in connection with the optical element shown in FIG.4).

The optoelectronic component 20 has a first electrical connectingconductor 205 and a second electrical connecting conductor 206. Thesepreferably project from the housing body at different side areasthereof. The connecting conductors serve for making electrical contactwith the semiconductor chip 3. The semiconductor chip 3 can beelectrically conductively connected to the first connecting conductor205 and/or be fixed thereon by means of a connection layer 207, forinstance an electrically conductive adhesive layer or a solder layer.The semiconductor chip is preferably conductively connected to thesecond connecting conductor 206 by means of a bonding wire 208.

The optoelectronic component 20, in particular the housing body, can beproduced by means of moulding encapsulation, for instance by means of aninjection moulding, transfer moulding or compression moulding method, ofa leadframe comprising the two connecting conductors 205 and 206 with asuitable moulding composition, for instance a plastic material, inparticular an epoxide- or acrylic-based material, for instance areaction resin. The semiconductor chip 3 can subsequently be connectedto the connecting conductors. The optoelectronic component canaccordingly have a premoulded housing, in particular a so-calledpremoulded package.

The housing body 203 preferably has a cavity 209, in which thesemiconductor chip 3 is arranged. Furthermore, an encapsulationcomposition 210 may be arranged in the cavity 209, the semiconductorchip 3 being embedded in said encapsulation composition. Thisencapsulation advantageously protects the semiconductor chip 3 and thebonding wire 208 from harmful external influences. By way of example,the encapsulation contains a reaction resin, for instance an acrylic orepoxy resin, a silicone resin or a silicone. The encapsulation ispreferably rigid in order to increase the protection.

The optoelectronic component may furthermore be formed for generatingmixed-colour, in particular white, light. For this purpose, part of theradiation generated by the semiconductor chip excites for example aluminescence conversion material (arranged in the encapsulationcomposition 210), for instance a phosphor, in particular in particleform, to emit longer-wave radiation. Mixed-colour, in particular white,light can consequently arise from the mixing of the radiation generatedby the semiconductor chip and the radiation reemitted by theluminescence conversion material. A primary radiation generated by thesemiconductor chip in the blue spectral range and a radiation reemittedby the luminescence conversion material in the yellow spectral range areparticularly suitable for generating white light.

The housing body 203 is preferably produced from a readily reflectivematerial, for instance white plastic. The walls of the cavity may becoated with a reflection-increasing material, for instance a metal, inorder to further increase the reflection of a radiation generated by thesemiconductor chip at the wall of the cavity. By means of reflection atthe wall of the cavity, the proportion of the radiation fed to theoptical element 2 for beam shaping can advantageously be increasedcompared with a housing body without a cavity 209.

The optoelectronic component is furthermore preferably formed insurface-mountable fashion (SMD: Surface Mountable Device). During thesurface mounting, by way of example, the connecting conductors 205 and206 are soldered onto conductor tracks of a printed circuit board (notillustrated) on the part of soldering areas 211 and 212 of theconnecting conductors.

If the optical element 2 is fixed at the optoelectronic component priorto the mounting of the latter, then the entire illumination device 1with the optoelectronic component 20 and the optical element 2 fixed atthe latter is embodied in surface-mountable fashion.

An intermediate layer 14 is arranged between the optical element 2 andthe semiconductor chip 3. The intermediate layer may adjoin theencapsulation 210 and, on the radiation entrance side, the opticalelement. The intermediate layer 14 may furthermore be embodied inplastically shapeable fashion.

The material of the intermediate layer is preferably embodied inadhesion-promoting fashion, thus increasing the mechanical linking ofthe optical element to the optoelectronic component.

Furthermore, the intermediate layer is preferably embodied as arefractive index adaptation layer, which reduces the jumps in refractiveindex experienced by radiation generated by the semiconductor chip 3prior to coupling into the optical element in comparison with an absentintermediate layer. By way of example, the optical element, theintermediate layer and the encapsulation composition may be coordinatedwith one another in such a way that the refractive indices of materialsadjoining one another, such as the refractive index of the encapsulationwith respect to that of the intermediate layer or that of theintermediate layer with respect to that of the optical element, are in aratio of 1.4:1.6 or less, for instance 1.4:1.48, with respect to oneanother. Reflection losses at interfaces are thus reduced.

The encapsulation, the intermediate layer and the optical elementpreferably contain a silicone. A refractive index adaptation can thus beeffected in a simplified manner.

The encapsulation and the optical element are preferably rigid comparedwith the intermediate layer, that is to say are embodied such that theycan be plastically formed only with a considerably higher expenditure offorce.

An intermediate layer containing a silicone gel, for instance SilGel 612from the company Wacker Chemie, in particular with a mixing ratio of thetwo components of approximately 1:1 (in this respect, cf. thecorresponding data sheet) is particularly suitable. A silicone gel, inparticular SilGel 612, may simultaneously have an adhesion-promotingeffect, be plastically shapeable and reduce jumps in refractive index.This holds true particularly if the encapsulation and/or the opticalelement contain a silicone.

The intermediate layer preferably completely covers the encapsulation210 and the region of the radiation entrance area 8 that is utilizedoptically for coupling in radiation, so that reflection losses atinterfaces are advantageously kept low.

In the event of heating, the intermediate layer can expand into aninterspace 15 formed between the optical element and the first main area202 of the housing body 203, as a result of which the mechanical loadingon the illumination device 1, in particular the encapsulation 210 andthe optical element, during temperature fluctuations is advantageouslykept low.

FIG. 7 illustrates an optoelectronic component that is particularlysuitable for an illumination device on the basis of a schematicperspective plan view of the optoelectronic component in FIG. 7A and aschematic perspective sectional view of the component in FIG. 7B.

An optoelectronic component of this type is described in more detail inWO 02/084749, for example, the disclosure content of which is herebyexplicitly incorporated by reference in the present application. Acomponent similar to that bearing the type designation LW W5SG(manufacturer: Osram Opto Semiconductors GmbH), a related component or asimilar component from the same manufacturer is particularly suitable asthe optoelectronic component.

The optoelectronic component 20 comprises a first electrical connectingconductor 205 and a second electrical connecting conductor 206, whichmay project from different side areas of the housing body 203 of theoptoelectronic component 20 and are formed for example wing-like.

The housing body 203 has a cavity 209, in which is arranged thesemiconductor chip 3 embedded in an encapsulation 210. The semiconductorchip 3 is electrically conductively connected to the connectingconductor 205 for example by means of a soldering connection. Aconductive connection to the second connecting conductor 206 is producedby means of the bonding wire 208. The bonding wire is connected to thesecond connecting conductor 206 preferably in the region of a bulge 213in a wall 214 of the cavity 209.

The semiconductor chip 3 is arranged on a thermal connection part 215,which functions as a chip carrier. The thermal connection part extendsin the vertical direction preferably from the cavity as far as thesecond main area 204 of the housing body 203 and facilitates alarge-are—in particular relative to the chip mounting area on thethermal connection part—thermal connection of the semiconductor chip 3on the part of the second main area to an external heat conductingdevice, for instance a heat sink e.g. made of Cu. The thermal loading onthe housing body can thus advantageously be reduced, particularly whenthe component is operated as a high-power component with a high-powersemiconductor chip, for instance a thin-film semiconductor chip (cf. thesemiconductor chip described in connection with FIG. 2). Theoptoelectronic component may be formed for generating a high radiationpower in conjunction with a heat dissipation that is advantageouslyimproved at the same time on account of the thermal connection part.Such an optoelectronic component is particularly suitable forilluminating areas, for instance for the backlighting of a displaydevice, for instance an LCD.

The thermal connection part is for example linked into a lug of thefirst connecting conductor 205 or connected in some other way to thefirst connecting conductor, in particular electrically conductivelyand/or mechanically, laterally peripherally connected. The secondconnecting conductor 206, which is provided for making contact with thebonding wire 208, is preferably elevated with regard to the chipmountingplane of the semiconductor chip 3 on the thermal connection part 215.The area of the wall of the cavity that is available for reflection ofradiation is thus advantageously kept large. Furthermore, the thermalconnection part itself may be embodied in reflective fashion and thenpreferably forms part of the bottom and/or the wall of the cavity. Thethermal connection part may furthermore project from the housing body onthe part of the second main area or terminate essentially in planarfashion with the housing body. By way of example, the thermal connectionpart contains a metal having a high thermal conductivity, for instanceCu or Al, or an alloy, for instance a CuW alloy.

A leadframe having the two connecting conductors 205 and 206 and thethermal connection part 215 can be surrounded with the material of thehousing body during the production of such an optoelectronic componentusing a suitable moulding method, for instance an injection mouldingmethod. The semiconductor chip is arranged at or in the premouldedhousing after the production of the housing body. The thermal connectionpart 215 is preferably formed with one or a plurality of bulges orprotrusions 216, thereby improving the mechanical linking of the thermalconnection part to the housing body and thus increasing the overallstability of the optoelectronic component.

Fixing devices 201 provided for fixing the optical element are formed onthe part of the first main area 202 of the housing body, it beingpossible for the optical element to be embodied for example inaccordance with the exemplary embodiments described further above. Forfixing the optical element at the housing body 203, four fixing devices201 may be provided, for example, which facilitate a mechanically stablefixing of the optical element at the component. The fixing devices 201are expediently arranged in the corner regions of the first main area202 of the housing body 203.

FIG. 8 shows, in FIGS. 8A to 8D, different schematic views of anoptoelectronic component and of an exemplary embodiment of anillumination device according to the invention. FIG. 8A shows a sideview of the optoelectronic component, FIG. 8B shows a plan view of theoptoelectronic component 20, FIG. 8C shows an oblique plan view of theoptoelectronic component from above, and FIG. 8D shows a side view ofthe illumination device 1 with the optical element 2 fixed at theoptoelectronic component. The optoelectronic component 20 shown in FIG.8 is embodied for example in accordance with the component described inconnection with FIG. 7.

In contrast thereto in accordance with FIG. 8, a material for theintermediate layer 14, for instance in drop or hemispherical form, isarranged on the encapsulation composition 210 arranged in the cavity209, said encapsulation composition preferably containing a rigidmaterial that protects the semiconductor chip and the bonding wire 208.The diameter B of the material for the intermediate layer is preferablyless than the diameter A of the cavity 209. The material of theintermediate layer 14 is in this case preferably formed in plasticallyshapeable fashion. By way of example, the material contains a siliconegel, for instance of the type mentioned further above. The material ofthe intermediate layer may be applied in the liquid phase to theoptoelectronic component and in particular the encapsulation composition210, for instance dropwise. It is preferably subsequently converted intoa solid, but still plastically shapeable phase. For this purpose, theoptoelectronic component may be heated, for example to a temperature of140 degrees, and the applied material of the intermediate layercrosslinks directly after application in a temperature-induced manner atleast partly in such a way that it is dimensionally stable andshapeable.

The material for the intermediate layer 14 preferably projects above thefirst main area 202 of the housing body 203. If the optical element 2,for instance the one illustrated in FIG. 4, is plugged onto theoptoelectronic component 20 from the side of the first main area 202 andsubsequently pressed on more extensively, then the radiation entrancearea 8 can come into contact with the material of the intermediate layer14. The pressure exerted distributes the material laterally, inparticular in a direction parallel to the first main area of the housingbody. The intermediate layer 14 is thereby formed, which is in directmechanical contact with the encapsulation 210 and the optical element.The cavity 209 is preferably completely covered by the intermediatelayer in the lateral direction. The optical linking of the semiconductorchip to the optical element is improved by such a large lateral extentof the intermediate layer 14.

The guide elements 10 are arranged laterally beside the side areas 217of the housing body. The guide elements preferably adjoin the housingbody in frictionally locking fashion. This increases the mechanicalstability of the optical element fixed at the optoelectronic componentand the overall stability of the illumination device 1.

The invention is not restricted by the description on the basis of theexemplary embodiments. Rather, the invention encompasses any new featureand also any combination of features, which in particular comprises anycombination of features in the patent claims, even if this feature orthis combination itself is not explicitly specified in the patent claimsor the exemplary embodiments.

1. An illumination device comprising an optoelectronic component havinga housing body and at least one semiconductor chip provided forgenerating radiation, and a separate optical element, which is intendedfor fixing at the optoelectronic component, said optical element havingan optical axis, the optical element having a radiation exit area andthe radiation exit area having a concavely curved partial region and aconvexly curved partial region, which at least partly surrounds theconcavely curved partial region at a distance from the optical axis, theoptical axis running through the concavely curved partial region,wherein the convexly curved partial region has a first region and asecond region, the curvature of the first region being less than thecurvature of the second region.
 2. Illumination device according toclaim 1, wherein-the semiconductor chip is embodied as a thin filmsemiconductor chip.
 3. An illumination device comprising; asemiconductor chip provided for generating radiation, and an opticalelement having an optical axis, the semiconductor chip being embodied asa thin film semiconductor chip, the optical element having a radiationexit area and the radiation exit area having a concavely curved partialregion and a convexly curved partial region, which at least partlysurrounds the concavely curved partial region at a distance from theoptical axis, the optical axis running through the concavely curvedpartial region, wherein the convexly curved partial region has a firstregion and a second region, the curvature of the first region being lessthan the curvature of the second region.
 4. Illumination deviceaccording to claim 3, wherein the illumination device comprises anoptoelectronic component having a housing body and the semiconductorchip, the optical element being embodied as a separate optical elementand the optical element being intended for fixing at the optoelectroniccomponent.
 5. Illumination device according to claim 1, wherein theoptical axis of the optical element fixed at the optoelectroniccomponent runs through the semiconductor chip.
 6. Illumination deviceaccording to claim 1, wherein the optical element is embodied inrotationally symmetrical fashion with respect to the optical axis. 7.Illumination device according to claim 1, wherein the convexly curvedpartial region has a curvature which is less than a curvature of theconcavely curved partial region.
 8. Illumination device according toclaim 1, wherein the convexly curved partial region has a surface areawhich is greater than the surface area of the concavely curved partialregion.
 9. The illumination device of claim 1, wherein the at least onesemiconductor chip provided for generating radiation is spaced apartfrom a radiation entrance area of the optical element.
 10. Illuminationdevice according to claim 1, wherein the housing body is prefabricatedand the semiconductor chip is subsequently arranged at the housing body.11. Illumination device according to claim 1, wherein the optoelectroniccomponent has a leadframe which is formed around, in particular aleadframe around which the housing body is formed.
 12. Illuminationdevice according to claim 1, wherein the optoelectronic component, inparticular the leadframe, has a first electrical connection part, asecond electrical connection part and a thermal connection part. 13.Illumination device according to claim 1, wherein the optoelectroniccomponent is embodied as a surface mountable component.
 14. Illuminationdevice according to claim 1, wherein the semiconductor chip comprises asemiconductor body arranged on a carrier and the semiconductor body hasa semiconductor layer sequence.
 15. Illumination device according toclaim 14, wherein the carrier is different from a growth substrate forthe semiconductor layer sequence.
 16. Illumination device according toclaim 14, wherein a mirror layer is arranged on the semiconductor body,in particular between the semiconductor body and the carrier. 17.Illumination device according to claim 16, wherein the mirror layercontains a metal.
 18. Illumination device according to claim 1, whereinthe optical element has at least one fixing element and the fixingelement is provided for fixing the optical element at the optoelectroniccomponent.
 19. Illumination device according to claim 18, wherein theoptoelectronic component, in particular the housing body, has at leastone fixing device and the fixing element for fixing the optical elementengages into the fixing device of the optoelectronic component. 20.Illumination device according to claim 1, wherein the optical element isprovided for fixing by means of press fit, hot press fit, caulking, hotcaulking, thermal riveting or adhesive bonding at the optoelectroniccomponent.
 21. Illumination device according to claim 18, wherein theoptical element has at least one guide element which, compared with thefixing element, is arranged closer to an edge delimiting the opticalelement on the part of the fixing element.
 22. Illumination deviceaccording to claim 21, wherein the guide element is embodied in bevelledfashion on a side remote from the edge.
 23. Illumination deviceaccording to claim 18, wherein the optical element has a plurality offixing elements and guide elements and the number of guide elements isgreater than the number of fixing elements.
 24. Illumination deviceaccording to claim 1, wherein an intermediate layer is arranged betweenthe optical element fixed at the optoelectronic component and thesemiconductor chip.
 25. Illumination device according to claim 24,wherein the intermediate layer is plastically shapeable. 26.Illumination device according to claim 24, wherein the intermediatelayer contains a silicone gel.
 27. Illumination device according toclaim 1, wherein an interspace is formed between the optical elementfixed at the optoelectronic component and the optoelectronic componentbetween that side of the housing body which faces the optical elementand the radiation entrance area.
 28. Illumination device according toclaim 27, wherein an intermediate layer is arranged between the opticalelement fixed at the optoelectronic component and the semiconductorchip, and wherein the interspace is provided as a gap for receiving theintermediate layer in the event of an expansion of the intermediatelayer.
 29. Illumination device according to claim 1, wherein thesemiconductor chip is embedded in an encapsulation.
 30. Illuminationdevice according to claim 24, wherein the semiconductor chip is embeddedin an encapsulation, and wherein the intermediate layer adjoins theencapsulation and the optical element.
 31. Illumination device accordingto claim 24, wherein the intermediate layer is formed as a refractiveindex adaptation layer.
 32. Illumination device according to claim 1,wherein the illumination device is provided for the backlighting of adisplay device, for instance of an LCD.
 33. Illumination deviceaccording to claim 21, wherein the optical element has a plurality offixing elements and guide elements and the number of guide elements isgreater than the number of fixing elements.
 34. Illumination deviceaccording to claim 29, wherein an intermediate layer is arranged betweenthe optical fixed at the optoelectronic component and the semiconductorchip, and wherein the intermediate layer adjoins the encapsulation andthe optical element.